Disorders of perception, attention, and memory frequently accompany the major mental diseases. To understand the neural mechanisms of these mental processes, we are recording the activity of neurons in the extrastriate and prefrontal cortex of monkeys engaged in tasks requiring visual discrimination, attention, and memory. Some inferior temporal neurons appear to function as adaptive mnemonic filters, whose response is suppressed according to the similarity of the present stimulus to both short- and long-term memory traces. As one gains experience with new stimuli, the pool of activated cells in inferior temporal cortex shrinks to just those cells carrying the most critical information, providing a possible basis for long-term memory. Other inferior temporal neurons can be "primed" by prefrontal mechanisms to detect a particular sought-for stimulus in a temporal sequence, providing a basis for working memory. During recall of stored memories, specific neurons in inferior temporal cortex and area V4 are reactivated, thereby segregating, or "labeling", the neurons providing the information needed for a given task. All of these mnemonic processes are engaged when searching a scene for a particular object, such as looking for a face in a crowd. In such a situation, mnemonic mechanisms in inferior temporal cortex appear to select the objects we attend to and foveate. More generally, they may select the objects acted upon by motor systems.